1. Technical Field
The present invention relates in general to integrated circuits and in particular to the manufacture of a capacitor within an integrated circuit substrate. Still more particularly, the present invention relates to a method for manufacturing a metal-to-metal capacitor utilizing only a single masking step.
2. Description of the Related Art
The fabrication of an integrated circuit within a semiconductor substrate typically requires a number of processing steps, including one or more masking steps to define features of integrated circuit components. A masking step entails a number of subsidiary steps, the first of which is coating the surface of the integrated circuit with photoresist. A photolithographic mask is then precisely aligned with the semiconductor substrate and irradiated with ultraviolet light to remove portions of the photoresist and thereby define the location of a component feature. The defined location of the component feature is then selectively processed by removing material (e.g., with an etchant) or adding material (e.g., by deposition or implantation). The masking step then concludes with the removal of the photoresist.
Conventionally, the fabrication of a metal-to-metal capacitor within an analog integrated circuit has required at least two masking steps, a first masking step that defines the location of the lower plate of the capacitor and a second masking step that selectively etches the deposited capacitor dielectric. The present invention recognizes that such masking steps are some of the most expensive steps in the fabrication process, particularly considering the cost of creating the photolithographic mask and the processing time required to perform subsidiary steps like aligning the mask and exposing the photoresist. Consequently, the present invention provides an improved method of fabricating an integrated circuit capacitor that requires only a single masking step.